The development of instrumentation techniques for research in internal combustion engines is described. A general discussion of instrument classification and requirements is followed by a description of transducer development including calibration techniques, signal processing, and data acquisition. Details are given of two direct on-line digitizing devices for high-speed data acquisition (one purpose made and the other using an on-line computer). An analaysis of instrumentation and data acquisition errors is presented. The integration of the data acquisition equipment into a semiautomatic controlled test bed is described and a proposal for a fully automated test bed presented. Appendices giving details of the basic principles of the operation and design considerations of the on-line computer facility for data acquisition and engine test bed control are included.